The present invention relates to elements sensitive to certain polluting organic compounds, in particular hydrocarbons, but also to some halogenated organic products, such as chloroform, trichlorethylene, allyl-chloride, and to oxygenated solvents, such as acetone and its derivatives, certain alcohols, and the like.
These elements are in particular suitable to form part of devices which comprise at least one element formed of a deteriorable material or, more generally, of a material whose mechanical characteristics are modified in contact with the polluting product.
These elements are, for example, pollution sensors wherein a pollution sensitive element is located in the area where pollution should be detected, for example in the vicinity of a pipe, on the surface of a body of water, or also in the atmosphere, this element co-operating with means adapted to actuate a visual and/or sound alarm when the sensitive element is deteriorated by the polluting product.
The invention is also applicable to automatic devices for fighting against pollution by putting into operation a suitable absorbing or neutralizing agent in the solid (powder), liquid or gaseous state. In such devices, the deterioration of a sensitive element upon contact thereof with the polluting agent will release the anti-pollution product.
However reference will be more particularly made in the following to the first indicated application, i.e. to the construction of pollution sensors, more specifically of devices capable of detecting the presence of polluting products, such as hydrocarbons, particularly on the surface of a water body.
The problem of pollution by hydrocarbons is indeed very important for everybody.
It is difficult, if not impossible, and always very expensive, once pollution is already present, to try fighting against its noxious and sometimes irreversible consequences.
A preventing action is necessary. Harbour equipments, refineries, airports, distribution circuits, require automatic pollution sensing devices which are both sensitive and reliable, to permit prevision of the steps to be taken when pollution is threatening.
This requires a system which is positioned at the locations where risks of leakage are found, or at places where hydrocarbons may flow.
This system must be adapted to remain at the same location in operative condition over a sufficient time interval, for example three months, so that its maintenance is not too burdensome, and to detect at any time the presence of hydrocarbons.
The problem to be solved is as follows:
1.degree./--At sea:
(a)--Detection of hydrocarbons in case of accident, so as to follow the evolution of the hydrocarbon layers. PA1 (b)--Detection of fraudulous hydrocarbon discharging. PA1 (a)--Detection of the presence of hydrocarbons in the cooling circuits, in the settling tanks, before discharging waste waters into water streams, PA1 (b)--Detection of hydrocarbon leakage from pipelines, fuel storage tanks, etc. . .
2.degree./--In a refinery:
There already exist automatic detection devices sensitive to certain polluting products, such as hydrocarbons, which comprise two sections of a strip or thread interconnected by means of a special glue which is deteriorated or dissolved by the polluting agent.
The assembly being kept under tension, the action of the polluting agent causes breaking of the assembly, thus triggering an alarm signal. Such devices have been for example manufactured by the Canadian Company Bennett Pollution Controls Ltd, under the name "Oil Spill Detection System".
Such a system is however difficult to produce and the results thereof are not very reliable, since the sensitivity of the gluing to the polluting agents highly depends on the quality of fabrication.
There also exist devices based on the use of a solid sensitive element, which, when contacted with polluting products becomes swollen or is destroyed, thereby causing the triggering of an alarm, as described in French Patent Application No. 2 178 950, German Patent Application Nos. 1 910 166 and 2 434 914 and Swiss Pat. No. 411 633.
The various products proposed heretofore to constitue the sensitive element are not fully satisfactory, either because they are not sensitive enough to the polluting products (as in the device of French Pat. No. 2 178 950), or, when sensitive enough, they cannot withstand for a sufficient time the action of light (as in the devices described in French Patent Application No. 2 254 749 and German Patent Application No. 2 434 914).
The invention provides a solid sensitive element which does not suffer from the above-indicated drawbacks.